Process for vulcanizing rubber and product obtained thereby



Patented Apr. 7, 1925.

SIDNEY M. CADWELL, OF LEONIA, NEW

PATENT OFFICE.

JERSEY, ASSIGNOR TO THE NAUGA TUCK CHEMICAL COMPANY, A CORPORATION OFCONNECTICUT.

IPROCESS FOR VULCANIZING RUBBER AND PRODUCT OBTAINED THEE-EBY. 0

No Drawing. Original, application filed April- 1, 1922, Serial No.548,826. Divided and this application filed April 1, 1922.

To all whome't may concern:

Be it known that I, SIDNEY M. CADWELL, a citizen of the United States,residing at Leonia, county of Bergen, and State of New Jersey, haveinvented certain new and useful Improvements in Processes forVulcanizing Rubber and Products Obtained Thereby, of which the followingis a full, clear, and exact description.

This invention relates to vulcanizing rubber and similar materials andproducts obtained thereby, being more particularly directed toacceleration of vulcanization by a class of organic accelerators andproducts resulting from such vulcanization.

This case is a division of application Serial No. 548,826 filed April 1,1922.

One object of the invention is to provide a process of the kindmentioned employing accelerators obtainable from inexpensive rawmaterials by a simple method. Another object of the invention is toprovide a process in which accelerators of the kind mentioned may bereadily compounded with rubber, or similar material, which shall permitof the carrying out of vulcanization at ordinary temperatures, in massesof rubber or in thin sheets while avoiding the generation of acidsduring the process of vulcanization, as, for example, takes place whensulphur chloride is used. Another object is to provide a series ofproducts having generally desirable, physical characteristics, such ashigh tensile strength, resistance to ageing, resistance to flexing,etc., and which 3 shall be substantially free from the odor of' thevulcanizing ingredients employed' Serial No. 548,829.

Other objects will in part be obvious and in part pointed outhereinafter.

' The invention accordingly consists broadly in the process and productobtained there-- from, for treating rubber and similar materials, whichcomprises subjecting the rubber a vulcanizing agent and a substancecontaining the radical RIOlSM,

and vulcanizing the rubber. In this formula, R represents any elementsubject to the limitation mentioned hereinafter; M represents asalt-forming element or group or hydrogen, such as zinc, ammonium, etc.,

and is designated as representing a metal or being metallic, or aradical S("JR or a radical (IJIR;

is limited to any element except nitrogen; in the third group Whererepresents CR I thislimitation is absent. In the table herein shownforming part of the specification, there is shown the broadgroup-containing the radical RCSM,

sub-divided. into three smaller groups which are respectively It will benoted that the group formulae represent generally derivatives of carbonoxysulphide or carbon disulphide.

The formulae of the first two groups mentioned, in which the firstsymbol R is any element except nitrogen, may be written under which anRGSM,

where M is the metal and thiol salts are included, and

n'osson, ll l where M is equal to son INC and the disulphides arerepresented. R in these formulae designate any element eX cept nitrogen.

In employing the first group of those mentioned above includingsubstances having the formula nous state, so that the preferred formulafor the thiol salts is where M represents one of the preferred metalsgiven. M may be substituted by any metal provided that one of the metalsjust mentioned is present in the combination, either at some otherposition in the formula including R R'psM or be introduced otherwisethan as part of this compound. In connection with the other groupsmentioned, namely, those represented by the formulae R'CSSCR and RCSGRllll XX constituting respectively the disulphide and monosulphidegroups, the presence of zinc or mercury in the mercuric state ispreferable when vulcanization at ordinary temperatures is carried out.When vulcanization above ordinary temperatures is car-- ried out thepreferred metals are the following :zinc, mercury, preferably in themercuric state, lead, preferably in the plumbous state, cadmium, copper,prefer-' ably in the cupric state, arsenic, preferably in the arsenousstate, manganese, preferably in the manganous state. As noted inconnection with the first group, the metals employed with groups 2 and 3may be present in any combined form.

In the table mentioned above, R and X are shown as. represented bycarbon, oxygen, nitrogen. and sulphur, which are four of the moreimportant elements occurring in organic compounds.

It will be understood that the invention is not limited to the speciesshown in the accompanying table, and that by substituting other elementsthan nitrogen, carbon, oxygen and sulphur for the symbol R or X, variousother species may be formulated falling within the scope of theinvention.

Although the various species disclosed are represented as symmetrical,it will be understood that unsymmetrical species also fall within thelimits of the invention.

The table is:

X M Metal Thiol Salts In general, it is to be noted in connection withthis group, that its members are able to accelerate both hotvulcanization, that is, vulcanization at or above 240 F. andvulcanization below such temperatures, and that they may be used forsuch vulcanization in thick masses of rubber, in thin sheets, or incements.

The general procedure for vulcanizing employing members of this group isas follows :1OO parts of rubber, 10 parts zinc oxide, 3 parts ofsulphur, and O.1-3.0 parts of accelerator are mixed. If hotvulcanization is employed the usual temperatures or lower may be usedfor periods of thirty minutes or more to complete vulcanization. Thenormal or usual temperatures of hot vulcanization are 240 F. or above.If cold vulcanization is desired the mixed materials may be allowed tostand at ordinary room temperature for a week on less, whenvulcanization is complete. The procedure given above may be employedwith thin or thick masses of rubber, and in the case of cements where asolvent is used with the mixture, the procedure after mixing andevaporation of the solvent, is substantially identical with thatemployed for thin masses of rubber.

The use of materials of this group, in the Y manner indicated above,will secure cold vulcanization without added bases or amines, but ifsuch bases or amines are added, the vulcanization is accelerated.

The action of the addition of amines to materials of this class has beenfound to be as follows :-The acceleration by aliphatic amines isgreatest when approximately a half molecular weight of the amine on thebasis of the carbon disulphide content of the thiol salt is used. Anexcess of primary aliphalic amine retards the cureconsiderably. Anexcess of secondary aliphatic amine retards the cure less and an excessof tertiary aliphatic amine has practically no retarding effect. Thegreater the amount of primary aromatic amine added the greater theacceleration. Dibenzyl amine has given excellent results in theacceleration of vulcanization according to the invention. Aniline hasalso given good results. Bases such as sodium hyldroxide also acceleratethe action of thiol sa ts.

The thiol salts are particularly adapted to be used in connection withcold curing and cements. It will be understood of course as pointed outabove that they may be used in hot vulcanization and otherwise asdesired. The members of the group are preferably employed withsubstances containing combined zinc, preferably zinc oxide, or one ofthe metals in combination hereinbefore enumerated. The oxides aregenerally designated as MO.

' Species 1.

oosM

[I s The followin members of this species have been employed to givegood results in connection with the process included in the inventionBarium ethylxanthogenatc C2H5OCSB3SCQ Calls ll g Sodiummethylxanthogcnate omm sm Lead methylxanthogenatc omocsrbsoocm Zincmethylxanthogenate CHaOCSZnSCQCHa t Lithium ethylxanthogenateCaHaOC'ESLI Ferric ethylxanthogenate onaioesre a Lead ethylxanthogenateozmocsrbscocm. ll I l Mercuric ethylxanthogenate oimocsn sooclrn gPotassium amylxanthogenate bonate Zinc amylxan'thogenateoinnoqsznsqonnoi Zinc ethylxanthogenate cimm isznscomo,

s Zinc butylxanthogenate omgoesz spoo'iu,

The following members of this species have been employed to give goodresults in connection withthe process included in the invent1on:

oimo' c i-sx Ethyloxyester of potassium thiolcar- Butyloxyester ofpotassium thiolcarbonate Species 3.

cost:

The following members of this species have been employed to give goodresults in connection with the'process included in the invention Ethylester of allyl thiocarbamic acid OlIz==OH-CH1NH' o==s I (321356 Ethylester of phenylthioc'arbamic acid cunNH o-s 021356 v Butyl ester ofphenylthiocarbamic acid i C((HBNH y 6=s c.1196" Speoies 5.

, CCSIM I ii,

The preferred member of this species is zine dithiobenzoate having'theformula CoHlCSZNSCCcHs- In employing this material the followingrocedure is carried out: 100 parts of ruber are mixed with 10 parts zincoxide, 3 parts sulphur, 1/10 part zine dithiobenzoate and vulcanizationis accomplished in a mold under 40 lbs. steam pressure for 30 minutes.

Zinc dithiobenzoate may be prepared by a standard method to be found inthe literature.. This method consists in dissolving brombenzol in dryethyl ether-and the solution is treated with magnesium turnings'. Aftercompletion of the reaction, carbon bisulphide is added and the solutionthus obtained is treated with water. The solution is extracted withether and the ether solution is extracted with sodium carbonate solutionin water. This solution is treated with zinc acetate and the zincdithiobenzoate separates as crystals and may be recovered.

For vulcanization at a temperature below the ordinary hot vulcanizingtemperature, such as at ordinary room temperature, 70 F. approximately,the following procedure is carried out: 100 parts ofrubber, 10 parts ofzinc oxide, 3 parts of sulphur, 3 parts of zinc dithiobenzoate, 2 partsof para toluidine are mixed on the mill and allowed to remam at ordinaryroom temperature for a Week or less whereupon satisfactory vulcanizationis effected. 1

As a specific example of the use of a member of this species inthe formof a cement, the following procedure is preferably carried out :-100parts of rubber, 20 parts of zinc oxide, and 6 parts of zincdithiobenzoate are mixed on the mill in the usual manner andsubsequently mixed with. 800 parts of benzol, thus forming one componentof the self-curingcement; 100 parts of "rubber, 3 parts ofdibenzylamine, and 6 parts of sulphur are mixed on the mill in the usualmanner and subsequently mixed with 800 parts of benzol to form thesecond component of the self-curing cement. Neither of these componentcements alone will cure quickly at ordinary or elevated temperatures. Ifequal parts of the component cements are mixed, the resulting cementwill cure in from 16 to 48 hours at ordinary room temperatures, or in ashorter time at elevated temperatures. If the solvent is allowed toevaporate from the cement the resulting rubber will cure in from 16 to48 hours at ordinary room temperatures, say 70 F. or at an elevatedtemperature, say 160 F. in the course of from l-to 2.hours. Othermembers of this species which have been employed to give good results inconnection with the process of the invention Lead dithiophenylacetateomomp-srbs-ocmom.

; connection with the process included in the or Thiobenzanilide Leaddlthlobenzoate COHONHCuHl CdIgCi-SPbS-CfllCoHs g Species .9.

or scsM Cadmium d1th1obenz0ate g c H G-SOdS-CC H u n 5 The followingmembers of this specles have been employed to give good results in orconnectlon with the process included 1n the Mercurous dithlobenzoate'1nVent1on:--

061150-8139; C;S1Cog( NH3)a K. A Hoffman & IIochtlen Borichte 36,1146(10))?! ll cobalto ammonium trithiocnrbonate CS3CuNHcnproammonimntrithiocarbonate (same ref.) K508; potassiumtrithiocurbonatc Cupric dithiobenzoate Basic calclum trlthlocarbonatecnHBp-sous-pom CQGOHMCaCS Species '10. or S(|I;SM Potassiumdithiobenzoate 0 f- The following member of this species has beenemployed to glve good results in conor nectlon with the process included1n thls 1n- Lead dithioacetate Vent1n:

CHaO-SPbS-CCH; Zinc dithiocarbonate ii zncos Species 13. Leaddlthlobrombenzoate A NCSM Brcnmo-sPbs-oommr l The members of this classinclude: Species 6. Potassmm orthomethylphenyleneditlnocarbamate II SThe following members of this species have been employed to give goodresults in connection with the process included in the 'Ammoniumpara-aminophenylenedithiocarbamate invention p NH2CoH4NHfi-SNHA Leadthiobenzoate I clmmspbswcam Ammonium phenylethyldithiocarbamate [I ll 0'0 N c SNH Potassium thioacetate, 02H? 11 .Potassmmpara-aminophenylenedithiocar- Lead thiobutrate bamate Z1ncpara-ammophenylened1th1ocarba- 817607168 7. mate f pNHaCuHaNHfiJ-S-Zn-S-(fiNHCaHANH: p

The following members of this species Z' t1 1 h ld'th' have beenemployed to give good results in me 6 W P any 1 locarb'amate invention zs I l g cins 'llhiobenzamide Ammonium benzidyldithiocarbamate Ammoniumphenyldithiocarbamate CQHINHC-SNHI Zinc phenylaminodithiocarbamate O HNHNHC-SZn-S-O-NHNHCuH:

Para methylphenyleneammonium' para methyiphenylenedithiocarbamate pCHaCuEhNH (fi-SHaNCoILCH; p

Ammonium meta methylaminophcnyldithiocarbamate Zincmetadiaminomethylphenyldithiocarbamate Ammonium paranitrophenylenedithiocarbamate p NO2CsH4NHC-SNH4 1 Ammonium para.methylphcnylenedithiocarbamate p CH3CH4NHFSNH4 Zinc paramethylphenylenedithiocarbamate Ammonium0rthomethylphenylenedithiocarba-mate Zinc phenylethylthiocarbamate Ce sCzH5

ll ll 0 0 'Zinc phenylmethyldithiocarbamate Stannousparamethylphenylencdithiocarbamate p. CHgCaH4NHfi3-SSfl/2 s Ironphenyldithiocarbamate combing-arm s .Zinc phenyldithiocarbamate ommmz-s-zn Iron ethylphenyldithiocarbamate CaH Bariumethylphenyldithiocarbamute Calcium e-thylphenyldithiocarbamate Paraaminophenyleneammonium paraammophenylenedithiocarbama te Barium bamate01'thomethylphenylenedithicar- Zinc 0rthomethylphenyle-ncdithiocarbamatei 0 CHaCuH4NHC-S-ZnSCNHCsH4OHz (o) g I Ferricparamethylphenylenedithiocarba;- mate Bariumparamethylphenylenedithiocarbamate p. CHaCaH4NHC-fi-B8/z Calciumparaimethylphenylenedithiocar- Zinc methylphenyldithiocarbamate Co sSpecies '14,

NOSM

' It Will be understood that the invention disclosed in co-pendingapplication Serial No. 441,691, filed February 1,1921, may be employedin connection with the accelerators disclosed and included in theinvention of the present application.

It is to be understood that rubber substitutes, synthetic rubber,balata, gutta percha, etc., may be similarly treated instead of rubberand it is intended to cover such processes in the claims.

In general the accelerators included in Group .1 given above areobtainable from in,- expensive raw materials by simple methods. Themembers of the group may be readily compounded with rubber or similarmaterial and may be employed generally in vulcanization in thin or thickmasses of rubber or in cements. It will be particularly noted that themembers of Group 1 are able to. accelerate vulcanization at temperaturesbelow the normal vulcanizing temperature, for instance at ordinary roomtemperature.

The ability to vulcanize at such temperature varies somewhat inaccordance with the the species selected.

The products obtained provide in general desirable physicalcharacteristics, such as high tensile strength, resistance to ageing,resistance to flexing, etc., and in general are free from the ordor ofvulcanizing ingredients. It will thus be seen that among others theobjects of the invention above enumerated are achieved.

Although described herein no other species is claimed except those inthe set made up of species 5, (3,7 and 8.

As many apparently widely dill'erent embodiments of this invention maybe made without departing from the spirit thereof, it will be understoodthat I do not intend to limit myself to the specific embodiment hereinset forth except as indicated in the appended claims.

Each of the substances enumerated herein as members of the variousspecies has been employed in the vulcanization of rubber and has beenfound to accomplish vulcanization as indicated.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A process of vulcanizing rubber or similar material which comprisescombining with the rubber a vulcanizing agent and an acceleratorcomprising the radical CCSM" where M is a metal, and vulcanizing therubber.

2. A process of vulcanizing rubber or similar material which comprisescombining with the rubber a vulcanizing agent and an acceleratorcomprising the radical and vulcanizing the rubber.

3. A process of vulcanizing rubber or similar material which comprisescombining with the rubber a vulcanizing agent and an acceleratorcomprising the radical cpsivi,

and vulcanizing the rubber.

4. A process of vulcanizing rubber or similar material which comprisescombining with the rubber a vulcanizing' agent and an acceleratorcomprising the radical CCSM,

. s and vulcanizing the rubber.

5. A process of vulcanizing rubber or similar material which comprisescombining with the rubber a vul-canizing agent, an acceleratorcomprising the radical ot sir ll X and vulcanizing the rubber atordinary temperatures.

8. A process of vulcanizing rubber or similar material which comprisescombining with the rubber a vulcanizing agent and an acceleratorcomprising the radical CCSM ll x in the presence of combined zinc, andvulcanizing the rubber.

9. A process of. vulcanizing rubber or similar material which comprisescombining with the rubber a vulcanizing agent and an acceleratorcomprising the radical ccsrr in the presence of combined zinc, andvulcanizing the rubber.

10. A process of vulcanizing rubber or similar material which comprisescombining with the rubber a vulcanizing agent, an accelerator"comprising the radical C(ESM in the presence of combined zinc, and anamine, and vul-canizing the rubber.

11. A process of vulcanizing rubber or similar material which comprisescombining with the rubber a-vulcanizing agent and an acceleratorcomprising the radical in the presence of combined zinc, and vulcanizingthe rubber at a temperature below the normal hot vulcamzing temperature.

12. A process of vulcanizing rubber or similar material which comprisescombining with the rubber a vulcanizing agent and an acceleratorcomprising the radical CCSM ll s 15. A process of vulcanizing rubber orsimilar material which comprises combining the rubber with sulphur, zincdithiobenzoate, and zinc oxide, and vulcanizing the rubber.

16. A process of vulcanizing rubber or similar material which comprisescombining the rubber with sulphur, zinc.- dithiobenzoate, zinc oxide andpara toluidine, and vulcanlzmg the rubber at ordinary telnperatures.

17. A vulcamzed rubber derived from rubber or s1m1lar material combinedwith a vulcaniz ng agent and an accelerator comprismg the radical OCHJSMx where M is-a metal.

18. A vulcanized rubber derived from rubber or similar material combinedwith a vulcamzmg agent and an accelerator comprising the radical 19. Avulcanized rubber derived from rubber or similar material combined witha vulcanizing agent and an accelerator com prising the radical cpsM.

20. A vulcanized rubber derived from rubber or s1m1lar material combinedwith a vulcanizmg agent and an accelerator compr sing the radical otisM'.

21. A vulcanized rubber derived from rubber or s1m1larmaterial-combinedwith a vulcamzing agent, an accelerator comprismg the radical ct zsivi XWhere M is a metal, and an amine. H

22. A vulcanized rubber derived from rubber or similar material combinedw th a vulcanizmg agent, a accelerator comprismg the radical and anamine.

23. A rubber vulcanlzed at ordinary temperatures derived from -rubber orSm ar materialcombined with a vulcanizing a ent' and an acceleratorcomprising the radical CIGISM.

24. A vulcanized rubber derived from rubber or similar material combinedwith a vulcanizing agent and an accelerator comprising the radical ccsMin the presence of combined zinc.

25. A vulcanized rubber derived from rubber or similar material combinewith a vulcanizing agent and an accelerator comprising the radical CCSMin the presence of combined zinc.

26. A vulcanized rubber derived from rubber or similar material combinedwith a vulcanizing agent, an accelerator comprising the radical I belowthe normal hot vulcanizing temperature derived from rubber or similarmaterial combined with a vulcanizing agent and an accelerator comprisingthe radical oc zsm I X in the presence of combined zinc.

28. A rubber vulcanized at a temperature below the normal hotvulcanizing temperature derived from rubber or similar material combinedwith a vulcanizing agent and an accelerator comprising the radical CCSMin the presence of combined zinc.

29. A rubber vulcanized at a temperature below the normal hotvulcanizing temperature derived from rubber or similar material combinedwith a vulcanizing agent, an accelerator comprising the radical in thepresence of combined zinc and an amine.

30. A vulcanized rubber derived from rubber or similar material combinedwith sulphurand zinc dithiobenzoate.

31. A vulcanized rubber derived from rubber or similar material combinedwith sulphur, zinc dithiobenzoate, and zinc oxide.

32. A rubber vulcanized at ordinary temperatures derived from rubber orsimilar material combined with sulphur, zinc dithiobenzoate, zinc oxideand para toluidine.

Signed at New York, this 30th day of March 1922.

SIDNEY M. CADWELL.

